1. Field of the Invention
The present invention relates to an aligner.
2. Related Art
A printed circuit board has become more compact and slimmer with downsizing electrical appliances and with decreasing their thicknesses. Recently, a photolithographic method is used as a technique for manufacturing printed circuit boards. An aligner as in the case of a semiconductor has been used to carry out a method for printing a circuit pattern patterned in a photo mask on a substrate which is an object to be exposed.
There are two methods of performing exposure while keeping the photo mask in contact with the object to be exposed and while keeping a photo mask away from contact with the object to be exposed. The former method needs uniform contact for exposure with high accuracy.
As a method to perform exposures with high accuracy, it has been proposed to evacuate a space between a photo mask and object to be exposed to force them into close contact with each other. However, in the case of a stepping exposure which has been proposed in recent years, it is relatively difficult to increase a vacuum level because a photo mask is smaller than the object to be exposed. Accordingly it is most suitable to use a so called soft contact method not including the forced-pressing as described above.
However in soft contact method without the forced close contact mentioned above, there has been a problem that it becomes very difficult to maintain the parallelisms of the photo mask and the object to be exposed and to maintain a uniform contact pressure.
The object of the invention is to solve the problems in connection with the related art described above.
To accomplish the objects, an aligner according to the invention is characterized by comprising: an object to be exposed supporting means for supporting an object to be exposed; a photo mask depicted with an exposure pattern; a photo mask supporting means for supporting the photo mask; a contact means for relatively bringing the object to be exposed supported by the object to be exposed supporting means and the photo mask supported by the photo mask supporting means closer and into contact with each other; and a pressure regulating means for regulating a contact pressure between the object to be exposed and photo mask. Such contact pressure regulating means makes it possible to properly maintain a contact pressure between the photo mask and an object to be exposed and thereby to perform exposures with high accuracy.
Also, in a preferred embodiment, the aligner further comprises a guide means for guiding a movement of the photo mask supporting means, and the guide means guides the photo mask supporting means and capable of sloping the photo mask supporting means, whereby it becomes possible to maintain the parallelisms of the photo mask and object to be exposed and to perform exposures with high accuracy.
In a preferred embodiment, when the contact pressure is predominantly created by a combined weight of the photo mask to be laid over the object to be exposed and the photo mask supporting means, a means for regulating the contact pressure may be arranged to regulate the contact pressure by regulating a load to the object to be exposed, which is generated by the combined weight.
Also, in a preferred embodiment, the photo mask supporting means may comprise a mask holder for mounting the photo mask, a copy frame for supporting the mask holder, and spacers interposed between the copy frame and mask holder to space them a given distance apart and to fix the mask holder to the copy frame at two locations, whereby the deformation of the photo mask can be suppressed.
Further, in a preferred embodiment, the photo mask may be provided with tapered portions in the periphery of the photo mask to provide an aligner suitable for step exposure.
In the case of stepping exposure, although the photo mask is smaller than the object to be exposed, the photo mask juts toward the object to be exposed compared to the photo mask supporting means, whereby the contact properties of the photo mask and the object to be exposed can be improved. To improve the contact properties, in a preferred embodiment, the photo mask is provided with tapered portions in the periphery of the photo mask, and supported by the photo mask supporting means at the tapered portions, which allows the photo mask to jut toward the object to be exposed with a maximum jutting height.